Among all the data storage solutions, the optical disks are becoming more and more important for backing up data and exchanging information because the optical disks have many advantages including a high storage capacity, easy to handle and carry, and a long preserving time for the stored data. Till now, the optical disk drives can be found all around us, such as in desktop computers, laptop computers, DVD players, and even some instruments or electronic products with built-in microprocessors.
Referring to FIGS. 1 and 2, perspective and exploded views of a conventional optical disk drive are shown to include a lower half casing 2, an upper half casing 6 coupled to the lower half casing 2 to form a casing 1, a chassis 4 disposed within the casing 1 for carrying a pick-up head thereon, a front panel 3 fixed to and covering the front open end of the casing 1, and a disk tray 5 disposed within the casing 1 above the chassis 4.
Referring to FIGS. 3, 4 and 5, top and perspective views of the lower half casing 2 are shown to include a gear transmission system 10 for driving the disk tray 5 (see FIG. 2) between an extended position, in which, the disk tray 5 extends outwardly from the casing 1 via an entrance-and-exit slot formed through the front panel 3, and a retracted position, in which, the disk tray 5 retracts inwardly into the casing 1 via the entrance-and-exit slot. The gear transmission system 10 includes a first gear 12, a gear transmission unit 101, a driven plate 13, and a lifting frame 7. The first gear 12 is disposed within the lower half casing 2. The gear transmission unit 101 includes a driving motor 11, a second gear 14 fixed co-axially on an output shaft of the driving motor 11, and a third gear 15 coupled to the second gear 14 via a plurality of transmission gears in such a manner that rotation of the second and third gears 14, 15 results in movement of the disk tray 5 between the extended and retracted positions. The driven plate 13 is disposed within the lower half casing 2 and extends in a transverse direction relative to a longitudinal axis of the lower half casing 2. The driven plate 13 is movable along the transverse direction to left and right sides of the lower half casing 2 (see FIGS. 8 and 6). The driven plate 13 has a first serrated portion 131 meshed with the first gear 12, and a second serrated portion 132 disposed adjacent to and facing the third gear 15. The driven plate 13 further has first and second guiding slots 133, 134, each of which is defined by a slot-confining wall. The lifting frame 7 is disposed within the lower half casing 2 at one side of the driven plate 13, and has first and second couplers 71, 72 slidably and respectively engaging with the slot-confining walls of the first and second guiding slots 133, 134 in the driven plate 13, and a protrusion 73. The lifting frame 7 is operably associated with the driven plate 13 in such a manner that movement of the driven plate 13 to the left and right sides of the lower half casing 2 results in movement of the lifting frame 7 to the upper and lower positions. The second serrated portion 132 of the driven plate 13 starts to engage with the third gear 15 during inletting of the disk tray 5 towards the retracted position.
When the disk tray 5 is at the extended position (not shown), the driven plate 13 is moved to the right side of the lower half casing 2, the first end 1311 of the first serrated portion 131 is meshed with the first end 121 of the first gear 12, the first end 1321 of the second serrated portion 132 is not engaged with the third gear 15 (see FIGS. 3 and 6) while the lifting frame 7 is in the lower position and the protrusion 73 of the lifting frame 7 does not abut against the driven plate 13. In the same manner, when the disk tray 5 is at the retracted position (not shown), the driven plate 13 is moved to the left side of the lower half casing 2, the second end 1312 of the first serrated portion 131 is meshed with the second end 122 of the first gear 12, the second end 1322 of the second serrated portion 132 is engaged with the third gear 15 while the lifting frame 7 is in the upper position and the protrusion 73 of the lifting arm 7 abuts against the driven plate 13 opposite to the second serrated portion 132 (see FIGS. 7 and 8).
In the aforesaid conventional disk drive, the second serrated portion 132 of the driven plate 13 is not constantly meshed with the third gear 15. The second serrated portion 132 is started to engage with the third gear 15 in the midway of the inletting process of the disk tray 5 so that the engagement between the first end 1321 and the third gear 15 could be improper. Thus, jamming of the second serrated portion 132 with respect to the third gear 15 may occur during the meshing operation. Moreover, after completing the inletting process of the disk tray 5, the second end 1322 of the second serrated portion 132 is engaged with the third gear 15, the third gear 15 would apply a force on the second end 1322 which may cause a break in the tooth of the second end 1322 due to abutment of the protrusion 73 against the driven plate 13 opposite to the second serrated portion 132.